The present invention relates generally to the field of radiating cables and more specifically to a flat, flexible radiating cable used as a transmitting and/or receiving antenna.
Radiating or xe2x80x9cleakyxe2x80x9d cables are well known in the art of radio transceivers. Flat radiating cables are also known. They are an alternative to coaxial radiating cables and especially well suited for certain applications where a low profile is desirable. Further, they are generally inexpensive to manufacture do to their simple construction.
Examples of flat radiating cables are disclosed in U.S. Pat. No. 2,800,634 to Grieg et al. and U.S. Pat. No. 6,081,728 to Stein et al. These prior art flat radiating cables all suffer from a common weakness. Such cables generally include a flexible dielectric core laminated between and adhered to two conductive layers, such as the flat cable 50 shown in FIG. 1.
A typical material which is used for the conductive layers is a metallic foil, such as copper. However, as illustrated in FIG. 2, when the cable 50 is flexed, kinks 52 may develop in the foil. This kinking effect is due, at least in part, to the differences in longitudinal compressibility between the various materials employed in the cable 50. Such kinks 52 have the adverse effect of significantly limiting the frequency response of the cable 50 at higher frequencies.
There is an increasing use of higher frequency transmission, such as in wireless data transmission. Thus, it would be desirable to provide a flat radiating cable for high frequency radio transmission and/or reception that is not prone to the frequency limiting kinks described above.
According to the present invention, a radiating cable is provided. The cable comprises a first layer comprising conductive material, a second layer comprising conductive material, and a dielectric layer being positioned between and adjacent to both the first layer and the second layer. At least one of the first layer and the second layer comprises a resilient material. Further, at least one of the first layer, the second layer, and the dielectric layer is movable relative to the other layers.